Coating composition



3,069,279 Patented Dec. 18, 1962 free 3,069,279 COATING COMPOSITEGNRobert A. Hartley, Mount Royal, Quebec, Alfred K.

Pester, Cartierville, Quebec, and James F. Hayes, Montreal West, Quebec,Canada, assignors to International Paints (Canada) Limited, Montreal,Quebec, Canada No Drawing. Filed Dec. 7, 1959, Ser. No. 857,583 6Claims. (Cl. 106-128) This invention relates to coating compositions andto methods of their preparation.

It has particular application to compositions of the general typedescribed in United States Patent 2,591,904 to John C. Zola dated April8, 1952, the disclosure of which is hereby incorporated by reference.Compositions of this type comprise a dispersion of particles of viscouscoating material in a water solution containing a colloidal suspensionstabilizer in an amount sufficient to prevent appreciable coalescencebut insufficient to cause emulsification of the particles. In thepatented composition most of the particles are said to exceed 50 micronsin size.

While compositions of this type have been found effective forapplication by spraying, difficulty has been experienced in applyingthem by painting roller coating. The applicants now provide compositionswhich are not fraught with this problem.

Fundamentally the applicants compositions have a consistency (viscosity)considerably higher than that of dispersions produced in accordance withthe aforesaid patent with a correspondingly large particle size. Theconsistency of the applicants compositions is above 65 Krebs units andis preferably below about 95 Krebs units. A preferred range is fromabout 77 to about 85 Krebs units. Thickening the consistency also hasthe effect of rendering the composition stickier which is an advantagefor application by roller. Raising the consistency without reducing theparticle size and without forming a stable emulsion is effectedaccording to a preferred phase of the present invention by incorporatingwith agitation over a short period of time enough additional protectivecolloid into the base dispersion to bring about the increasedconsistency. Preferably this agitation is equivalent to that broughtabout by mixing in a twoor three-bladed propeller-type mixer at about150' to about 350- r.p-.m. for a time within the range from about lminute to about 3 minutes. This contrasts with the agitation usuallyemployed during the preparation of the base dispersion in whichagitation takes place equivalent to mixing for about 20 to about 30minutes in a lightning type v trasted with lab scale mixing in which themixing speed and time might differ.

Temperature also has a bearing on the resulting composition. Mixing cantake place within a temperature range from about- 35' F. to about 100 F.Elongated particles'which are desirable are produced when the mixing iseffected within the range from about 70 F. to about 80 F. A certainamount of particle size control can therefore be exercised by varyingthe temperature. The applicants have found that in their compositionsmost of the particles as in Zola are above 50 microns and many are above100 microns, some go up to 5000 microns.

In the mixing, care should also be taken to' avoid blending of therespectivephases atthe outset and before agitationcommences. In thisconnection the applicants prefer to add the liquid phase to the lacquerphase in making the base composition by pouring it on in a layer andthen to start the agitation. In other words, the lacquer is added to theaqueous phase one colour at a time and it is necessary to splash some ofthe aqueous phase over each colour to prevent amalgamation of thecolours from occurring. If the lacquer phase is added during agitation,-then the particle size will vary considerably. When the additionalcolloid or other additive is added, this may be accomplished whileagitation is taking place and the addition is done slowly. I

Thus, according to a preferred method of the invention, the basecomposition is made according to the teachings of United States Patent2,591,904. Then, the protective colloid is added under the conditionsabove described. The applicants have also found that a still furtherimprovement in the nature of the resulting composition can be broughtabout if the protective colloid is present in a synthetic resin emulsionor paint. Therefore, a preferred phase of the invention is to add,instead of a protective colloid alone, a synthetic resin emulsion orpaint in which such colloid is present. If desired, a combination ofprotective colloid and synthetic resin emulsion or paint may beemployed.

The applicants have found that contray to the experience with the basedispersion, a modified composition as above described can be applied bya painting roller as well as by spraying, preferably a painting rollerhaving a coarse, tufted texture. The applicants have found it of decidedadvantage to use a roller which is covered by textile fabric being an 18pick frieze, with a mohair-rayon blend face, and a cotton backing coatedwith neoprene latex. And, a .075 inch gaugepile wire is used in makingthe fabric. In using the roller it is desirable to keep it uniformly andfairly heavily loaded and to roll it gently but firmly on the surface.It is of advantage to work in a small area, for example 2-foot squares,applying the coating evenly in a vertical direction and then to roll thesame area with horizontal strokes. The globules which appear afterrolling will flatten as they dry. The composition may also be applied byconventional spray equipment or a vacuum cleaner spray attachment.

It is also desirable to first coat the surface with a sealer. This hasthe advantage of obliterating previously painted surfaces and producinga more pleasing effect. The colour of the sealer should be similar tothe basic colour of the paint. The sealer also acts to provide a uniformsuction over the entire surface and hence prevents shadows or highlightscaused by joints, nailheads or other unevennesses.

ADDITIVES Effective additives are the materials usually classified underthe heading of organic or synthetic hydrophilic or protective colloids.The applicants have found the following. hydrophilic colloids areeffective and are preferably employed within the range of concentrationstated,

by dry weight of the finished composition.

Percent Methyl cellulose (4000 centipoises) 0.7 to'2 Glue l to 2Dextrine 6 to 16 Casein- 1 to2 Hydroxyet-hyl cellulose 0.3 to'0;6Carooxymethyl cellulose 0.3 to 0.6

The hydrophilic colloid is first put into equeous solution and thissolution is added to the base composition in the manner described-above.

The applicants have found that preferred results are achieved by addingthermoplastic synthetic resin emulsions or paints which contain thecolloid. Polyvinyl acetate emulsions or paints are preferred,particularly the paints. Emulsions or paints of butadiene-styrene,polyacrylates and other polyvinyl esters, for example polyvinylpropionate may be employed.

The characteristics of these emulsions that are necessary in order thatthey function according to the invention are that the emulsion bestable. They can be an emulsion alone or pigmented so as to constitutepigmented emulsions or actual compositions which are known commerciallyas emulsion paints. Generally speaking these paints contain pigment inan amount which will give from about to about 40% by volume of pigmentin the dry volume. This is generally an amount in excess of by weight inthe paint. Generally speaking the solids in the emulsion will run fromabout to about 55% when it is not pigmented and from about 20% to about40% in the case of a paint. The emulsion or emulsion paint type ofadditive should be added to the base composition in an amount within therange from about 3% to about 20% by weight with 5% to about 10%preferred.

The quality of the composition for use in roller coating can be testedby trying the composition with a roller. Compositions containinginsutficient colloid will smear whereas in compositions containing anexcess of colloid there is a tendency of the particles to break downprematurely due to shearing action.

The applicants have found that inorganic colloidal materials in thenature of fullers earth, talc, barium sulfate, calcium carbonate,calcium sulfate, magnesium carbonate and diatomaceous earth are notdesirable for the purposes of the invention.

The presence or absence of other materials and the amounts of thesematerials will have a bearing on the properties of the composition. Forexample, the solvents used in the lacquer phase are preferablyhydrophobic or there is a tendency of the emulsions to break down.Preferred solvents are methyl amyl acetate, amyl acetate and ethyl amylketone.

The proportions of solvents employed in the lacquer phase is preferablywithin the range from about 60% to 70% by weight of the total lacquerphase. The ratio of coating material to the aqueous is within the range2.75:1 to 3.25:1. The specific gravity of the lacquer phase ispreferably controlled to be Within the range from about 1.003 to about1007 so that the above mentioned proportions hold true even if thelacquer phase is considered by weight instead of by volume.

The applicants can use the standard pigments as prescribed in theafore-mentioned Zola Patent. Pigments should be used which are insolublein lacquer type solvent.

The applicants have generally described the invention and will now giveexamples of specific, preferred formulations and procedures in orderthat the invention be more fully understood.

Example I The following is an example of the preparation of a typicalcoating composition in accordance with the invention.

A base composition according to United States Patent 2,591,904, wasprepared by mixing the following constituents:

These constituents were mixed together in a threebladed propeller typemixer at a mixing speed of 300 r.p.m. for minutes.

A polyvinyl acetate paint additive was prepared according to thefollowing formulation. made of the following constituents:

The mixture was Rutile titanium dioxide (pigment) 252 Tributyl phosphate(anti-foaming agent) 1 /2 Polyvinyl acetate emulsion (CRC emulsion F 20)(plasticized with dibutylphthalate) 314 CRC emulsion F 60 (plasticizedwith dibutylphthalate) 314 Water (to adjust viscosity to between 72 to76 Krebs units) 30 This mixture was ground on a Morehouse mill. Theresulting additive was mixed with the base composition at 250 r.p.m. for3 minutes. Most of the particles in the composition exceeded 50 micronsin size and the composition was relatively stable.

The composition was applied using a roller of the characteristicsdescribed above. The resulting coating had excellent covering power andadhesion to the surface.

Example II Another composition was prepared in which the basecomposition contained the following constituents:

Pounds 1% methyl cellulose solution 74 Water 141 First coloured lacquer108 Second coloured lacquer 615 These constituents were dispersed usinga three-bladed propeller type mixer' operating at 250 r.p.m. for about30 minutes. Then, 83 pounds of 2% methyl cellulose solution were addedand the composition stirred for 3 minutes at 300 r.p.m.

An excellent coating composition resulted which was applicable with aroller to form good coatings.

Example III A base composition was prepared having the followingconstituents:

Pounds 1% methyl cellulose solution 74 Water 73 First coloured lacquer72 Second coloured lacquer 217 Third coloured lacquer 434 The basiccomposition was prepared by dispersing the constituents with athree-bladed propeller type mixer operating at 350 r.p.m. for 20 minutesand then the following modifying substances were added while mixing at300 r.p.m. for 2 minutes.

Pounds Polyvinyl propionate dispersion (Propiofan 5 D) 55 1% methylcellulose solution 45 An excellent coating composition resulted whichwas applicable with a roller to form good coatings.

Example IV A base composition was prepared having the followmgconstituents:

Pounds 1% methyl cellulose solution 74 Water 101 First coloured lacquer687 Second coloured lacquer 36 These constituents were dispersed as inExample I and there was then added 122 pounds of a 37.5% dextrinesolution and the mixture was stirred for 2 minutes at 300 r.p.m.

An excellent coating composition resulted which was applicable with aroller to form good coatings.

In all the examples the film has a mottled effect. The colours can bechanged by varying the concentration of the coloured lacquers within theranges stated. It is also possible to change the size and shape byvarying the concentration of protective colloid and the viscosity of thelacquer phase within the limits given.

We claim:

I. A multiple step process for preparing an aqueous dispersion of acoating composition having a viscosity adapted for roller coating ofsurfaces which comprises:

as a first step, forming an aqueous dispersion of discrete largeparticles of a viscous hydrophobic coating material most of which arelarger than 50 microns under strenuous dispersing conditions includingvigorously agitating a viscous hydrophobic coating material over anextended period of time with a colloidal solution of a quantity of anorganic hydrophilic protective colloid suflicient to maintain said largeparticles in the dispersed state Without substantial coalescence butinsuflicien-t to substantially further reduce the sizes of saidparticles under the conditions aforesaid to provide thereby an aqueousdispersion having a viscosity consistency below 65 Krebs units; and as asecond step, introducing into the formed aqueous dispersion additionalquantities of an organic hydrophilic protective colloid suflicient toincrease the viscosity of theresulting aqueous dispersion to betweenabout 77 to 95 Krebs units under substantially less strenuous dispersingconditions including agitation tor a substantially shorter period oftime sufiicient to term thereby a homogeneous dispersion of theadditional colloid but insufi'icient to substantially reduce the sizesof said large particles; the total amount of protective colloid beingsufiicient to substantially decrease the sizes of said large particlesunder the dispersing conditions of said first step.

2. The process of claim 1 wherein the dispersing conditions in the firststep is equivalent to that of a lightning type mixer at a speed fromabout 250 to about 350 r.p.m. for a time from about to about 30 minutesand the dispersing conditions in the second step is equivalent toagitation with a lightning type mixer at a speed from about 150 to about350 r.p.m. for a time from about 1 minute to about 3 minutes.

3. The process of claim 1 wherein the hydrophilic protective colloid isa resin.

4. The process of claim 1 wherein particles of a difierent color aredispersed in said first step.

5. The composition prepared according to the process of claim 1.

6. A multiple step process for preparing an aqueous dispersion of acoating composition having a viscosity adapted for roller coating ofsurfaces which comprises:

as a first step, forming an aqueous dispersion of discrete largeparticles of a viscous hydrophobic coating material most of which arelarger than 50 microns under strenuous dispersing conditions includ ingvigorously agitating a viscous hydrophobic coating material underconditions equivalent to that of a lightning type mixer at a speed fromabout 250 to about 350 r.p.m. for a time from about 20 to about 30minutes with a colloidal solution of a quantity of an organichydrophilic protective colloid sutficient to maintain said largeparticles in the dispersed state without substantial coalescence butinsufiicient to substantially further reduce the sizes of said particlesunder conditions aforesaid to provide thereby an aqueous dispersionhaving a viscosity consistency below Krebs units; and

as a second step, introducing into the formed aqueous dispersionadditional quantities of an organic hydrophilic protective colloidsufiicient to increase the viscosity of the resulting aqueous dispersionto a viscosity substantially above 65 Krebs units under substantiallyless strenuous dispersing conditions including agitation equivalent toagitation with a lightning type mixer at a speed from about 4150 toabout 350 r.p.m. for a time from about 1 minute to about 3 minutes toform thereby a homogeneous dispersion of the additional colloid withoutsubstantially reducing the sizes of said large particles;

the total amount of protective colloid being sufficient to substantiallydecrease the sizes of said large particles under the dispersingconditions of said first step.

References Cited in the file of this patent UNITED STATES PATENTS

1. A MULTIPLE STEP PROCESS FOR PREPARING AN AQUEOUS DISPERSION OF ACOATING COMPOSITION HAVING A VISCOSITY ADAPTED FOR ROLLER COATING OFSURFACES WHICH COMPRISES: AS A FIRST STEP, FORMING AN AQUEOUS DISPERSIONOF DISCRETE LARGE PARTICLES OF A VISCOUS HYDROPHOBIC COATING MATERIALMOST OF WHICH ARE LARGER THAN 50 MICRONS UNDER STRENUOUS DISPERSINGCONDITIONS INCLUDING VIGOROUSLY AGITATING A VISCOUS HYDROPHOBIC COATINGMATERIAL OVER AN EXTENDED PERIOD OF TIME WITH A COLLOIDAL SOLUTION OF AQUANTITY OF AN ORGANIC HYDROPHILIC PROTECTIVE COLLOID SUFFICIENT TOMAINTAIN SAID LARGE PARTICLES IN THE DISPERSED STATE WITHOUT SUBSTANTIALCOALESENCE BUT INSUFFICIENT TO SUBSTANTIALLY FURTHER REDUCE THE SIZES OFSAID PARTICLES UNDER THE CONDITIONS AFORESAID TO PROVIDE THEREBY ANAQUEOUS DISPERSION HAVING A VISCOSITY CONSISTENCY BELOW 65 KREBS UNITS;AND AS A SECOND STEP, INTRODUCING INTO THE FORMED AQUEOUS DISPERSIONADDITIONAL QUANTITIES OF AN ORGANIC HYDROPHILIC PROTECTIVE COLLOIDSUFFICIENT TO INCREASE THE VISCOSITY OF THE RESULTING AQUEOUS DISPERSIONTO BETWEEN ABOUT 77 TO 95 KREBS UNITS UNDER SUBSTANTIALLY LESS STRENUOUSDISPERSING CONDITIONS INCLUDING AGITATION FOR A SUBSTANTIALLY SHORTERPERIOD OF TIME SUFFICIENT TO FORM THEREBY A HOMOGENOUS DISPERSION OF THEADDITIONAL COLLOID BUT INSUFFICIENT TO SUBSTANTIALLY REDUCE THE SIZES OFSAID LARGE PARTICLES; THE TOTAL AMOUNT OF PROTECTIVE COLLOID BEINGSUFFICIENT TO SUBSTANTIALLY DECREASE THE SIZE OF SAID LARGE PARTICLESUNDER THE DISPERSING CONDITIONS OF SAID FIRST STEP.